Chemical coordination

Glands in our body are of two types:

•Exocrine glands
•Endocrine glands

Exocrine glands are those which pour their secretions into a duct. For example, sweat glands,
tear glands, etc.

Endocrine glands are the ductless gland those which are richly supplied with blood vessels and
pour their secretions (Hormones) directly into the blood vessels. For example, thyroid, adrenal,
etc.
 Hormones

Definition:
Hormones are non-nutrient chemicals which act as intercellular
messengers and are produced in trace amounts.

Discovery of Hormones: William M Bayliss and Ernest H Starling.

 Characteristics of Hormones:
• they may be proteinaceous or non-proteinaceous (amino acids or
steroids)

• they are secreted as per need and not stored, only excreted

• their secretion may be regulated by nerves or by feedback effect

• they are transported by blood

• they mostly cause long-term effects like growth, change in

behaviour, etc.

• they do not catalyse any reactions

• they function as chemical messenger by stimulating or inhibiting

the target organs.
 Classification
I. On the basis of Chemical nature:

•Amino acid derivatives : Epinephrine and nor-epinephrine

(catecholamines, tyrosine derivative), Melatonin (tryptophan derivative),
Dopamine (tyrosine derivative).
• Iodothyronines: Thyroxine (tyrosine derivative) = Amino acids + Iodine,
•Steroids : They are cholesterol derivative, e.g., Estrogen, progesterone,
testosterone, hormones of adrenal cortex and calcitriol.

•Peptides ADH, oxytocin

•Proteins :, ACTH, GH, MSH, prolactin, hypothalamic hormones, Insulin,
glucagon, renin, relaxin, parathyroid hormone, calcitonin, Intestinal
hormones and ANF of heart.

•Fatty acids : Prostaglandins (from seminal vesicles, kidney or neural

tissues).

•Glycoproteins : TSH, FSH and LH.

 Classification
1. Tropic Hormone : The hormones which control the functional activities of
other endocrine glands. eg. ACTH, TSH, FSH, LH
2. Synergistic hormone:Work together. Eg. LH and FSH
Hypothalamu

Anterior pituitary
LH FSH

Leydig cells Sertoli cell

Testosterone Androgen Binding Protein

Stimulate spermatogenesis
Classification

3. Antagonistic Hormone: Work against each other. Eg

a. Insulin and Glucagon
b. Calcitonin and parathormone

4. Neuroendocrine hormones are secreted by neurons into the circulating blood and
influence the function of cells at another location in the body. Eg
a. ADH b. Oxytocin c. hypophysiotropic hormones

5. Local Hormone (tissue hormone, parahormone) are secreted by tissue but work on
adjacent tissue. Eg. a. testosterone, b. gastrin, c. secretin
 Mechanism of Hormone action
Hormone Receptors and Their Activation
The first step of a hormone’s action is to bind to specific receptors at the target
cell.

Cells that lack receptors for the hormones do not respond.

When the hormone combines with its receptor, this usually initiates a cascade
of reactions in the cell, with each stage becoming more powerfully activated so
that even small concentrations of the hormone can have a large effect.

Hormonal receptors are large proteins, and each cell that is to be stimulated
usually has some 2000 to 100,000 receptors.

Also, each receptor is usually highly specific for a single hormone; this
determines the type of hormone that will act on a particular tissue.

The target tissues that are affected by a hormone are those that contain its
specific receptors.
 Mechanism of Hormone action

The locations for the different types of hormone receptors are generally the
following:
1.In or on the surface of the cell membrane. The membrane receptors are
specific mostly for the protein, peptide, and catecholamine hormones.

2. In the cell cytoplasm. The primary receptors for the different steroid
hormones are found mainly in the cytoplasm.

3. In the cell nucleus. The receptors for the thyroid hormones are found in the
nucleus and are believed to be located in direct association with one or more of
the chromosomes.
 Mechanism of Hormone action

1. Mechanism of action of water soluble hormone (second messenger

hypothesis of Southerland)
1. Adenylate Cyclase-cAMP second messenger system. Eg. ACTH
2. Phospholypase C second messenger system eg Angiotensin II

2. Mechanism of action of lipid soluble hormone eg Testosterone

 1. Adenylate Cyclase-cAMP second messenger system.

Cyclic
adenosine
monophosph
ate (cAMP)
mechanism
by which
many
hormones
exert their
control of cell
function.
ADP,
adenosine
diphosphate;
ATP,
adenosine
triphosphate.
Mechanism of activation of a G protein–coupled receptor. When the hormone
activates the receptor, the inactive α, β, γ G protein complex associates with
the receptor and is activated, with an exchange of guanosine triphosphate
(GTP) for guanosine diphosphate (GDP). This causes the a subunit (to which
the GTP is bound) to dissociate from the β and γ subunits of the G protein and
to interact with membrane-bound target proteins (enzymes) that initiate
intracellular signals.
 1. Phospholypase C second messenger system eg Angiotensin II
The cell
membrane
phospholipid
second
messenger
system by
which some
hormones
exert their
control of cell
function. DAG,
diacylglycerol;
IP3, inositol
triphosphate;
PIP2,
phosphatidylin
ositol
biphosphate.
 Mechanism of action of lipid soluble hormone

Mechanisms of interaction of lipophilic hormones, such as steroids, with intracellular

receptors in target cells. After the hormone binds to the receptor in the cytoplasm or in the
nucleus, the hormone-receptor complex binds to the hormone response element (promoter)
on the DNA. This either activates or inhibits gene transcription, formation of messenger RNA
(mRNA), and protein synthesis.
One hormone, different effects. Epinephrine, the primary “fight-or-flight”
hormone, produces different responses in different target cells. Target cells with
the same receptor exhibit different responses if they have different signal
transduction pathways and/or effector proteins; compare (a) with (b). Responses
of target cells may also differ if they have different receptors for the hormone;
compare (b) with (c).
 Endocrine Location Embryonic origin
Glands
Pituitary Just below the Ecto derm , The anterior
(Hypophysis hypothalamus pituitary originated from
cerebri) (It is situated in the sella Rathke’s pouch, and
(Smallest endocrine turcica of sphenoid of the posterior pituitary from
gland) skull) neural tissue outgrowth from
hypothalamus
Thyroid Side of trachea Endoderm
(largest endocrine
gland)

Parathyroid The posterior surface of Endoderm

the lobes of the thyroid
gland
Adrenal The top of the kidneys Adrenal cortex– mesoderm
Adrenal medulla-
neuroectodem
Pineal gland Dorsal side of fore brain Ectoderm
(Epiphysis
cerebri)

Thymus In the upper part of the Endoderm

thorax near the heart
Pancreas Inferior to the stomach Endoderm
in a bend of the
duodenum
Ovaries In the pelvic cavity in Mesoderm
close proximity to the
oviducts and uterus
Testes In the scrotum of male Mesoderm
HYPOTHALAMUS
Hypothalamus is the floor of diencephalon which controls the secretion of pituitary
gland
Hormones of Hypothalamus :

Types Example Target Released hormone

Releasing hormones GnRH Pituitary Gonadotropins
TSH-RH Thyroid Thyroxine
Inhibiting hormone Somatostatin Pituitary -
Pituitary
Hypothalamus Hypothalamus
Neurons

Connected
Connected through stalk but not via through portal
portal circulation circulation

Anterior
Posterior pituitary pituitary

Store and releases

hypothalmic hormones

Pars nervosa Pars distalis

Pars intermedia

Neurohypophysis
Adenohypophysis
Endocrine glands and hormone secreted from them

• Anterior pituitary
– Growth hormone
– Thyroid-stimulating hormone (TSH)
– Adrenocorticotropic hormone (ACTH)
– Prolactin
– Follicle-stimulating hormone (FSH)
– Luteinizing hormone (LH)

Cells and Hormones of the Anterior Pituitary Gland and Their Physiological Functions

Acidophil

Chromaphobes

Basophil

Acidophil
• Posterior pituitary
– Antidiuretic hormone (ADH) (also called vesopressin)
– Oxytocin
Functions of Hormones secreted from Anterior pituitary

Hormones of Anterior Basic Functions

pituitary
Growth hormone Stimulates body growth

Thyroid-stimulating Synthesis and Stimulation of production of thyroid

hormone (TSH) hormones
Adrenocorticotropic Stimulates production of glucocorticoids and androgens by
hormone (ACTH) the adrenal cortex
Follicle-stimulating Male: regulates spermatogenesis in the testis
hormone (FSH) Female: Stimulates development of ovarian follicles

Luteinizing hormone Male: stimulates testosterone (androgens) production by the

(LH) testis
Female: Causes ovulation and formation of the corpus
luteum in the ovary; Stimulates production of estrogen and
progesterone by the ovary
Prolactin (PRL) Stimulates milk secretion and production
Functions of Hormones secreted from Pars intermedia

Hormones Basic Functions

Melanocyte Acts on the melanocytes of skin and regulates pigmentation
stimulating of skin.
hormone (MSH)

Functions of Hormones secreted from Posterior pituitary (neurohypophysis)

Hormones Basic Functions

Oxytocin • Acts on smooth muscles and stimulate their contraction.
• Stimulate vigorous contractions of uterus at the time of child birth.
• Stimulates milk ejection from breasts.

Antidiuretic • Acts at kidney and stumulates reabsorption of water and

hormone(ADH) electrolytes by the distal tubules.
• Reduces loss of water through urine (Diuresis).
 Disorders
Hormones Disorders Characters
Growth Hypo Dwarfism Deficiency of growth from childhood.
Hormone secretion
Gigantism (in Excess of growth.
Hypersecre childhood)
tion Acromegaly (in Disproportionate increase in size of bone of
adult) face, hand & feet's.
ADH Hypo Diabetes insipidus Excessive excretion of dilute urine.
secretion
Thyroid Glands
• Thyroid
– Thyroxine = Tetraiodothyronine (T4) ( 93%) and triiodothyronine (T3) (7%=
more active than T4)
– Calcitonin Calcitonin =
T3 and T4 Thyroid calcitonin

Parathyroid
Parathyroid hormone (PTH)
Parafollicular cells

Parathormone =
parathyroid
calcitonin
Functions of Hormones secreted from Thyroid
General Information:
•Located Side of trachea.
•Bilobed structure and connected by Isthmus.
•Iodine is essential for normal rate of hormone synthesis in the hydroid gland.

Hormones Basic function

1. Regulate basal metabolic rate (BMR).
Thyroxine and
2. Control metabolism of carbohydrates ,
Triiodothyronine proteins and fats.
(together known as 3. Maintain water and electrolyte balance.
Thyroid hormones) 4. Regulate development and maturation of
CNS.
5. Support the erythropiesis.
6. Regulate menstrual cycle.

Thyrocalcitonin 1. It increases Ca2+excretion. Deposit within

Hormone (TCT) : bone
2. It checks osteoporosis.
3. Bone become solid and strong.
 Functions of Hormones secreted from Parsthyroid

Hormones Basic function

parathormone or • Increase level of Ca2+ (hypercalcemic).

parathyrocalcitonin • Acts on bones and stimulates the process of
hormone (PTH) bone resorption.
• Stimulate the reabsorption of Ca2+ by the renal
tubules.
• Increases Ca2+ absorption from digested food.
 Hormones Disorders Characters
Thyroxin Cretinism (in infant) Slow body growth and mental development.
Myxoedema (in adult) Puffy appearance due to accumulation of fat due to low
Hypo secretion (Gull’s disease) metabolic rate.

Simple Goiter Thyroid enlargement (Deficiency of I2 leads to inhibit

synthesis of thyroid hormones)
Hypersecretion Exophthalmic goiter Exophthalmia.
(Grave’s disease)

Parathyroid Hypo secretion Parathyroid tetany This increases the excitability of nerves & muscles, causing
cramps and convulsion.
Hypersecretion Osteoporosis Bones become deformed & are easily fractured.
Adrenal gland
Functions of Hormones secreted from Adrenal cortex

Hormone Functions
Cortisols
• Stimulate gluconeogenesis, Lipolysis and proteolysis.
(Glucocorticoids)
• Inhibit cellular uptake and utilisation of amino acids,
maintains the cardiovascular system and the kidney
function.
• has anti-inflammatory effects.
• Stimulate GFR.
• Stimulate RBC production.

Aldosterones • Increases renal sodium and water reabsorption,

(Mineralocorticoids) • potassium secretion,
• hydrogen ion secretion

Androgenic steroid Play a role in growth of axial hair , pubic hair during
puberty.
• Adrenaline and noradrenaline
– adrenaline is an important hormone as it causes 'fight or flight
response'.
– This means that it prepares the body to react in emergency
situations by various means like selective dilation and constriction
of blood vessels, increase in glucose levels (for more energy),
raising blood pressure.
 Hormones Disorders Characters
Cortisols Hypo secretion Addison’s disease Low blood sugar, low plasma Na+. High K+, nausia, vomiting
& Aldosterone & diarrhoea

Aldosterone Hypersecretion Aldosteronism low plasma Na+. High K+, rise in blood volume & pressure
Gonadocorticoid Hypersecretion Adrenal Virilism Appearance of male characters in female.
(Androgen)
PINEAL GLAND
 PINEAL GLAND

•Ectodermal in origin.
•It is composed of modified nerve cells - pinealocytes.
•It degenerates after seven years. In adult it is replaced by fibrous tissue.
•It accumulates Ca and Mg salts forming "Brain sand".

Hormones :
•Melatonin= controls body’s DIURNAL RHYTHM
Influence the body metabolism, temperature,
pigmentation, menstrual cycle and defense capability.
•Serotonin : It acts as vasoconstrictor
Schematic of the insulin receptor. Insulin binds to the a-subunit of its receptor, which
causes autophosphorylation of the b-subunit receptor, which in turn induces tyrosine
kinase activity. The receptor tyrosine kinase activity begins a cascade of cell
phosphorylation that increases or decreases the activity of enzymes, including insulin
receptor substrates, that mediate the effects of glucose on glucose, fat, and protein
metabolism. For example, glucose transporters are moved to the cell membrane to
facilitate glucose entry into the cell
Basic mechanisms of glucose stimulation of insulin secretion by
beta cells of the pancreas. GLUT, glucose transporter.
Endocrine glands and hormone secreted from them Pancreatic juice secretion

• Pancreas
– Insulin (β cells)
– Glucagon (α cells)
– Somatostatin (delta cells)
Functions of Hormones secreted from Pancreas

• Insulin (β cells)
– Promotes glucose entry in many cells, and this way controls
carbohydrate metabolism.
• Glucagon (α cells)
– Increases synthesis and release of glucose from the liver into the body
fluids
• Somatostatin (delta cells)
• Inhibits the secretion of Insulin and glucagon.
 Islet of Langerhans :
•αcells (oxyphil cells, become red with Mallory - Azan dye) secrete Glucagon.
•βcells (Basophil cells, become orange with Mallory ‑ Azan dye), secrete Insulin.
•γ cells (become blue with Mallory - Azan dye) secrete Gastrin.
•δ cells secrete Somatostatin.
•F cells secrete Pancreatic peptide.
Disorders :
Diabetes mellitus : Caused by hyposecretion of insulin.
Symptoms of diabetes mellitus are
•Hyperglycaemia : High blood glucose level (> 150 mg / 100 ml.)
•Glycosuria : Glucose in urine.
•Polyuria : Excessive urination, dehydration, loss of electrolytes.
•Polydipsia : Excessive thirst.
•Reduced storage of fat and protein synthesis.
•Oxidation of fatty acids and aminoacids is inhibited.
•Acidosis and ketone body formation is increased.
•Wasting of body tissues.
•Healing power of wound is reduced.
•Resistance of the body to infection is reduced.
Diabetic coma : Unconsciousness and may be followed by death. It occurs due to ketoacidosis + dehydration +
hyperglycaemia.
Insulin shock : If insulin is injected after excessive exercise or after delayed meal, blood sugar falls quickly (upto 30 mg / 100
ml of blood). Patient become unconscious or may die.
Types of Diabetes mellitus
•Insulin dependent IDDM TYPE I: It occurs due to insulin deficiency. 0 cells do not produce insulin properly.
•Insulin independent INDDM = TYPE II: Recessive autosomal disorder, Cells fail to take up insulin from blood mainly
due to defective insulin receptor on plasma membrane of liver cells. More in INDIA
 Hormones Disorders Characters
Insulin Hypo secretion Diabetes mellitus High blood glucose level
Hypersecretion Hypoglycemia Low blood glucose level
GONADS
Functions of Hormones secreted from Testes
• Testosterone = Interstitial cells of Leydig = Interstitial space of Seminiferous tubules
– Promotes development of male reproductive system and male
secondary sexual characteristics.
– Stimulate spermatogenesis.
– Stimulate muscular growth, growth of facial and axial hair,
aggressiveness and low pith of voice.
– Produce anabolic effect on protein and carbohydrate metabolism.
Functions of Hormones secreted from Ovary
• Estrogens = Membrena granulosa and Zona interna of Graafian follicle and Corpus luteum
– Promotes growth and development of female reproductive system,
female breasts, and female secondary sexual characteristics.
• Progesterone = Secreted from corpus luteum
– Supports pregnancy.
– Stimulates formation alveoli and milk secretion.
Thymus
THYMUS GLAND
•Endodermal in origin.
•It is partly endocrine, partly lymphoid.
•It is nearest to heart, located in the superior and anterior mediastinum of the thoracic
cavity and is behind the manubrium of the sternum.
•It plays an important role in immunity.
•In man and mammals, it is present between pericardium and upper part of sternum.
•At the age of 15-16 years this gland remains largest in size but later on gradually
atrophies due to activity of sex glands.
•It is made up of two lobes held together by connective tissues. The gland contains
lymphoid tissue that forms T-lymphocytes (for immunity). Epithelial cells occur in the
medulla and are called Hassall's concentric corpuscles (phagocytic).

Hormones :

Thymosin or thymin : It helps in deposition of mineral salts on the bones,

accelerates cell division and lymphocyte formation,
increases resistance,
inhibits maturation of sex glands.

Disorders :
Enlarged thymus may cause myasthenia gravis, acromegaly, Grave's disease and
Addison's disease. Removal of this gland retards growth, bones become soft.
 Hormonal disorders
Hormones Disorders Characters
Growth Hormone Hypo secretion Dwarfism Deficiency of growth from childhood.
Gigantism (in childhood) Excess of growth.
Hypersecretion Acromegaly (in adult) Disproportionate increase in size of bone of face, hand &
feet's.
ADH Hypo secretion Diabetes insipidus Excessive excretion of dilute urine.

Thyroxin Cretinism (in infant) Slow body growth and mental development.
Myxoedema (in adult) Puffy appearance due to accumulation of fat due to low
Hypo secretion (Gull’s disease) metabolic rate.

Simple Goiter Thyroid enlargement (Deficiency of I2 leads to inhibit

synthesis of thyroid hormones)
Hypersecretion Exophthalmic goiter Exophthalmia.
(Grave’s disease)
Parathyroid Hypo secretion Parathyroid tetany This increases the excitability of nerves & muscles, causing
cramps and convulsion.
Hypersecretion Osteoporosis Bones become deformed & are easily fractured.
Cortisols Hypo secretion Addison’s disease Low blood sugar, low plasma Na+. High K+, nausia, vomiting
& Aldosterone & diarrhoea

Aldosterone Hypersecretion Aldosteronism low plasma Na+. High K+, rise in blood volume & pressure
Gonadocorticoid Hypersecretion Adrenal Virilism Appearance of male characters in female.
(Androgen)

Insulin Hypo secretion Diabetes mellitus High blood glucose level

Hypersecretion Hypoglycemia Low blood glucose level
 Hormones Target cells
Growth hormone Cells which undergo growth
Thyroid-stimulating hormone (TSH) Cells of thyroid
Adrenocorticotropic hormone (ACTH) Cells of adrenal cortex
Prolactin Cells of mammary gland
Follicle-stimulating hormone (FSH) Cells of gonad
Luteinizing hormone (LH) Cells of gonad
Antidiuretic hormone (ADH) Cells of Kidneys
Oxytocin Cells of mammary gland
Thyroxine (T4) and triiodothyronine (T3) Cells of the body tissues
Calcitonin Cells of the bone (osteocytes)
Cortisol (Glucocorticoid) Cells of liver
Aldosterone (Mineralocorticoid) Cells of Kidneys
Gonadocorticoid Cells of gonad
Adrenaline Cells of skeleton, cardiac & smooth
muscle, blood vessels and fat cells.
Insulin Cells of Live , muscles & adipose tissues
Glucagon Cells of Live & adipose tissues
Somatostatin Cells of pancreas
Parathyroid hormone (PTH) Cells of the bone . Kidney & liver.
Testosterone Cells of gonads, cells related to growth
Estrogens Cells of placenta, Ovaries, uterus
Progesterone Cells of placenta, Ovaries, uterus